1. Field of the Invention
The present invention relates in general to manual antenna alignment techniques for a very small aperture terminal (VSAT), and more particularly to manual antenna alignment apparatus and method for the very small aperture terminal in which an antenna can easily be aligned with a satellite even by an unskilled man with no use of costly, additional equipment such as a special alignment device, a spectrum analyzer and etc.
2. Description of the Prior Art
Generally, an antenna is essentially used in a satellite communication system such as a very small aperture terminal to receive a feeble signal of a high frequency transmitted from a satellite. The level of the feeble signal received by the antenna depends on the linearity of the antenna and the satellite. For this reason, the antenna must accurately be aligned with the satellite to receive correct data without any noise.
The antenna used in the very small aperture terminal is very small in size. For example, such an antenna may be an offset feed type parabola antenna with a length of 1.2 m or 1.8 m.
Antenna alignment is initially performed when the very small aperture terminal is installed. Conventionally, the antenna alignment is performed by an antenna alignment expert using costly, additional equipment such as a spectrum analyzer, a special alignment device and etc.
In such a conventional antenna alignment method, a low-noise block down converter (LNB) is mounted to the antenna. An output of the low-noise block down converter is connected to the special alignment equipment or the spectrum analyzer. Under this condition, the antenna alignment expert observes the level of the signal being transmitted from the satellite, while moving a reflector of the antenna. During the observation, the antenna alignment expert adjusts the reflector of the antenna in such a manner that the maximum level signal can be received.
However, the above-mentioned conventional antenna alignment method is not economical because it requires the costly, additional equipment. Also, the antenna alignment expert must continuously observe the level of the signal being transmitted from the satellite to fix the antenna to a point that the maximum level signal is received. As a result, much time is required in aligning the antenna with the satellite.
On the other hand, a portable antenna alignment apparatus is disclosed in U.S. Pat. No. 5,019,833. The portable antenna alignment apparatus comprises a low-noise block down converter, a portable satellite television receiving antenna for receiving a television broadcasting wave signal from a satellite, an alignment device for adjusting an angle of the antenna according to a predetermined value to align the antenna with the satellite, and cover and base housing sections for containing the alignment device therein. When the antenna is not used, it is disconnected from a parabolic reflector and contained in the base housing section, which is then coupled with the cover housing section. Therefore, the user can easily carry the portable antenna alignment apparatus.
The above-mentioned conventional antenna alignment apparatus has the advantage of providing the user with convenience because it can be easily carried by the user. However, the above-mentioned conventional antenna alignment apparatus does not relate to a technique in which an inexpensive and simple circuit construction is provided in the very small aperture terminal to allow even an unskilled man to align the antenna with the satellite while observing the level of the signal being transmitted from the satellite with the naked eye and to reduce the cost resulting from the use of special and additional equipment.